Summary of Significant Accounting Policies - Revenue (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Disaggregation of Revenue [Line Items]
Revenues	$ 12,008	$ 11,994	$ 9,313
Avis
Disaggregation of Revenue [Line Items]
Revenues	6,779	6,519	4,894
Budget
Disaggregation of Revenue [Line Items]
Revenues	4,478	4,701	3,715
Other
Disaggregation of Revenue [Line Items]
Revenues	751	774	704
Americas
Disaggregation of Revenue [Line Items]
Revenues	9,347	9,474	7,557
Europe, Middle East and Africa
Disaggregation of Revenue [Line Items]
Revenues	2,014	1,927	1,400
Asia and Australasia
Disaggregation of Revenue [Line Items]
Revenues	$ 647	$ 593	$ 356